This study will evaluate any differential effects of four antihypertensive agents on Left ventricular hypertrophy (LVH) in African Americans and the prognostic impact of LVH regression on fatal coronary heart disease, nonfatal myocardial infarction, cardiovascular mortality and morbidity. Specific Aims: 1) Determine the prevalence of left ventricular hypertrophy by electrocardiography (ECG) compared to echocardiography in ALLHAT participants. 2) Determine the relationship of LVH regression on arrhythmia prevalence and severity on 24 hour ambulatory ECG monitor. 3) Compare the predictive accuracy of ECHO vs. ECG left ventricular hypertrophy for ALLHAT endpoints of fatal coronary heart disease, nonfatal myocardial infarction, cardiovascular mortality, cardiovascular morbidity and all cause mortality. Methods: Study Population - 475 patients enrolled in the NHLBI sponsored Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) will be recruited. Patients will be randomized per ALLHAT protocol to chlorthalidone (control group), lisinopril and doxazocin for blood pressure control with five to seven year follow up. Baseline, and annual 12 lead ECG will be performed to determine ECG-LVH. Baseline, Year 1, midpoint (Year 3 or 4), endpoint (Year 5 ,6, or 7)echocardiograms will be performed for analysis of LV mass, wall thickness, wall stress and indices of diastolic function. 24 hour ambulatory ECGs will be recorded at the time of echocardiography for assessment of ventricular arrhythmia. ALLHAT outcome measures of all cause mortality, fatal and nonfatal myocardial infarction, stroke, congestive heart failure, LVH and medical care utilization costs by each blood pressure drug will be ascertained throughout the study. Analysis: Between group comparisons for outcome measures will be made in addition to comparisons of the predictive and prognostic accuracy of LVH measured by ECG vs. ECHO.